The primary aim of the proposed work is to develop microelectrodes for determining if nasal membrane cholesterol is elevated in human cystic fibrosis. Studies will calibrate the electrodes through solution experiments and validate this calibration using a new proposed influx titration assay where the electrode is used as an indicator of influx. Human studies using the electrodes will involve single cell studies on epithelial cells from nasal scrapes. In vivo electrode measurements in the human nose are also proposed. In developing the measurements as a diagnostic tool, implementation of in vitro measurements at cells and mouse tissues is proposed to establish the relationship between CFTR function and plasma membrane cholesterol content.